1. Field of the Invention
The invention relates to fabrication of microlens arrays and its application to produce long period gratings.
2. Description of Prior Art
The invention relates more particularly to methods of producing a low cost microlens array with a length longer than 200 mm. Chosen forms of those microlens arrays are, according to this invention, used to write long period gratings with germanosilicate fibres, which fibres are themselves readily commercially available. Hitherto such long period gratings have been normally produced by using amplitude masks that must selectively blocks off laser radiation leading to inefficient use of power. Commercial micro-optics arrays constructed with UV grade fused silica is an alternative as it focuses the laser beam into a periodic pattern and thus requires much less energy from the laser. Unfortunately, the extremely high cost of such microlens arrays normally prohibits their use in long period grating fabrication.